Mix mild detergent or non-detergent soap and cold water (30℃ – 40℃) thoroughly. Do not use the alkaline detergent, it will damage the filling power of down. Do not use bleach agent or softener, it will affect the fabric breathable function.
Place the jacket into the water and push under and squeeze out as much air as you can. Down is very buoyant and floats high on top of water, it may take a little work but it's worth it. Then wash the dirty marks.

Rising thoroughly.
Drip dry in shade. Avoid direct sunlight to dry.
Gently padding while drying until it becomes light and fluffy.

Finish the pre-soak process or if you have a pre-soak cycle on your machine use that instead. Start the machine and complete the washing cycle

Dryer set on LOW temperature (about 40℃), dry for about 15-20 minutes. Then gently padding on the jacket and hanging until 80% dry. Put into the dryer again until its light and fluffy. You can also put a tennis ball into the dryer to make the down jacket more fluffy. Or after put it in the dryer, you can hanging under the dehumidifier to dry.

Down jacket must dry thoroughly when store , if not it become moldy and derived bacteria.
When down jacket take out from cabinet, you can put it into the dryer in low temperature for 10 minutes to make it back to it shape.